Submersible mixing impellers are known devices with a wide variety of applications for introducing a fluid, such as a gas or liquid, into the liquid in which the device is submerged. For example, they are used to draw air from the atmosphere into a liquid to aerate the liquid.
In the field of organic waste treatment, decomposition of organic matter, such as vegetable wastes and sewage, can be effected by introducing suitable bacteria into a tank containing a slurry of the organic matter in water, while aerating and mixing the slurry. Thorough aeration of the slurry, in the form of fine air bubbles dispersed throughout the slurry, accelerates such decomposition by providing ample oxygen to the bacteria.
Slurries of organic matter typically contain solid matter, namely the organic matter itself or trash such as wrapping materials, which are frequently made of plastic, that accompany the waste. To prevent blockages within the aerator, it is important that it function in a manner which does not draw the slurry into the aerator during the aeration process. It is also desirable for the aerator to draw sufficient air into itself for aeration of the slurry by the simple rotation of the aerator, without the need for any external pump to supply air to the aerator. It is also desirable for the aerator to disperse the drawn air into the slurry as fine bubbles. A need therefore exists for an improved aerator for use in aerating waste slurries.